Gas turbine engine airfoil

ABSTRACT

An airfoil for a turbine engine includes an airfoil that has pressure and suction sides that extend in a radial direction from a 0% span position at an inner flow path location to a 100% span position at an airfoil tip. The airfoil has a relationship between a leading edge dihedral and a span position. The leading edge dihedral is negative from the 0% span position to the 100% span position. A positive dihedral corresponds to suction side-leaning, and a negative dihedral corresponds to pressure side-leaning. The airfoil has a relationship between a trailing edge dihedral and a span position. The trailing edge dihedral is positive from the 0% span position to the 100% span position. A positive dihedral corresponds to suction side-leaning and a negative dihedral corresponds to pressure side-leaning.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/876,995 filed on Oct. 7, 2015 which is a continuation of U.S.application Ser. No. 14/624,025 filed on Feb. 17, 2015 which is now U.S.Pat. No. 9,353,628 issued May 31, 2016, which claims priority to U.S.Provisional Application No. 61/942,025 filed on Feb. 19, 2014.

BACKGROUND

This disclosure relates generally to an airfoil for gas turbine engines,and more particularly to leading and trailing edge aerodynamic dihedralrelative to span for gas turbine engine blades.

A turbine engine such as a gas turbine engine typically includes a fansection, a compressor section, a combustor section and a turbinesection. Air entering the compressor section is compressed and deliveredinto the combustor section where it is mixed with fuel and ignited togenerate a high-speed exhaust gas flow. The high-speed exhaust gas flowexpands through the turbine section to drive the compressor and the fansection. The compressor section typically includes low and high pressurecompressors, and the turbine section includes low and high pressureturbines.

The propulsive efficiency of a gas turbine engine depends on manydifferent factors, such as the design of the engine and the resultingperformance debits on the fan that propels the engine. As an example,the fan may rotate at a high rate of speed such that air passes over thefan airfoils at transonic or supersonic speeds. The fast-moving aircreates flow discontinuities or shocks that result in irreversiblepropulsive losses. Additionally, physical interaction between the fanand the air causes downstream turbulence and further losses. Althoughsome basic principles behind such losses are understood, identifying andchanging appropriate design factors to reduce such losses for a givenengine architecture has proven to be a complex and elusive task.

SUMMARY

In one exemplary embodiment, an airfoil for a turbine engine includes anairfoil that has pressure and suction sides that extend in a radialdirection from a 0% span position at an inner flow path location to a100% span position at an airfoil tip. The airfoil has a relationshipbetween a leading edge dihedral and a span position. The leading edgedihedral is negative from the 0% span position to the 100% spanposition. A positive dihedral corresponds to suction side-leaning, and anegative dihedral corresponds to pressure side-leaning. The airfoil hasa relationship between a trailing edge dihedral and a span position. Thetrailing edge dihedral is positive from the 0% span position to the 100%span position. A positive dihedral corresponds to suction side-leaningand a negative dihedral corresponds to pressure side-leaning.

In a further embodiment of the above airfoil, the leading edge dihedralat the 0% span position is in the range of −3° to −12°.

In a further embodiment of any of the above airfoils, the leading edgedihedral at the 0% span position is about −4°.

In a further embodiment of any of the above airfoils, the leading edgedihedral at the 0% span position is about −10°.

In a further embodiment of any of the above airfoils, the leading edgedihedral extends from the 0% span position to a 20% span position andhas a leading edge dihedral in a range of −2° to −6°.

In a further embodiment of any of the above airfoils, the leading edgedihedral includes a first point at a 75% span position and extendsgenerally linearly from the first point to a second point at the 85%span position.

In a further embodiment of any of the above airfoils, the first point isin a range of −8° to −10° dihedral.

In a further embodiment of any of the above airfoils, the second pointis in a range of −3° to −6° dihedral.

In a further embodiment of any of the above airfoils, a maximum negativedihedral is in a range of 95-100% span position.

In a further embodiment of any of the above airfoils, a least negativedihedral is in a range of 5-15% span position.

In a further embodiment of any of the above airfoils, a maximum negativedihedral is in a range of 65-75% span position.

In a further embodiment of any of the above airfoils, a least negativedihedral is in a range of 0-10% span position.

In a further embodiment of any of the above airfoils, a maximum negativedihedral is in a range of 50-60% span position.

In a further embodiment of any of the above airfoils, the relationshipprovides a generally C-shaped curve from the 0% span position to a 50%span position and then a 90% span position.

In a further embodiment of any of the above airfoils, a trailing edgedihedral at the 0% span position is in a range of 20° to 25°.

In a further embodiment of any of the above airfoils, a trailing edgedihedral at about the 50% span position is in a range of 2° to 6°.

In a further embodiment of any of the above airfoils, a trailing edgedihedral at the 90% span position is in a range of 16° to 22°.

In a further embodiment of any of the above airfoils, from a 65% spanposition to a 75% span position the trailing edge dihedral increasesabout 5°.

In a further embodiment of any of the above airfoils, a positive-mosttrailing edge dihedral in a 80%-100% span position is within 5° of thetrailing edge dihedral in the 0% span position.

In a further embodiment of any of the above airfoils, a least positivetrailing edge dihedral is in a 40%-55% span position.

In a further embodiment of any of the above airfoils, the airfoil is afan blade for a gas turbine engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be further understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 schematically illustrates a gas turbine engine embodiment.

FIG. 2A is a perspective view of a portion of a fan section.

FIG. 2B is a schematic cross-sectional view of the fan section.

FIG. 2C is a cross-sectional view a fan blade taken along line 2C-2C inFIG. 2B.

FIG. 3A is a schematic view of fan blade span positions.

FIG. 3B is a schematic representation of a dihedral angle for anairfoil.

FIG. 4A illustrates a relationship between a leading edge aerodynamicdihedral angle and a span position for a set of first example airfoilsand a prior art curve.

FIG. 4B illustrates a relationship between a trailing edge aerodynamicdihedral angle and a span position for a set of first example airfoilsand a prior art curve.

FIG. 5A illustrates a relationship between a leading edge aerodynamicdihedral angle and a span position for a set of second example airfoilsand a prior art curve.

FIG. 5B illustrates a relationship between a trailing edge aerodynamicdihedral angle and a span position for set of second example airfoilsand a prior art curve.

The embodiments, examples and alternatives of the preceding paragraphs,the claims, or the following description and drawings, including any oftheir various aspects or respective individual features, may be takenindependently or in any combination. Features described in connectionwith one embodiment are applicable to all embodiments, unless suchfeatures are incompatible.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmenter section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flow path B in abypass duct defined within a nacelle 15, while the compressor section 24drives air along a core flow path C for compression and communicationinto the combustor section 26 then expansion through the turbine section28. Although depicted as a two-spool turbofan gas turbine engine in thedisclosed non-limiting embodiment, it should be understood that theconcepts described herein are not limited to use with two-spoolturbofans as the teachings may be applied to other types of turbineengines including three-spool architectures. That is, the disclosedairfoils may be used for engine configurations such as, for example,direct fan drives, or two- or three-spool engines with a speed changemechanism coupling the fan with a compressor or a turbine sections.

The exemplary engine 20 generally includes a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis X relative to an engine static structure 36 viaseveral bearing systems 38. It should be understood that various bearingsystems 38 at various locations may alternatively or additionally beprovided, and the location of bearing systems 38 may be varied asappropriate to the application.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a first (or low) pressure compressor 44 and afirst (or low) pressure turbine 46. The inner shaft 40 is connected tothe fan 42 through a speed change mechanism, which in exemplary gasturbine engine 20 is illustrated as a geared architecture 48 to drivethe fan 42 at a lower speed than the low speed spool 30. The high speedspool 32 includes an outer shaft 50 that interconnects a second (orhigh) pressure compressor 52 and a second (or high) pressure turbine 54.A combustor 56 is arranged in exemplary gas turbine 20 between the highpressure compressor 52 and the high pressure turbine 54. A mid-turbineframe 57 of the engine static structure 36 is arranged generally betweenthe high pressure turbine 54 and the low pressure turbine 46. Themid-turbine frame 57 further supports bearing systems 38 in the turbinesection 28. The inner shaft 40 and the outer shaft 50 are concentric androtate via bearing systems 38 about the engine central longitudinal axisX which is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The mid-turbine frame 57 includes airfoils 59 whichare in the core airflow path C. The turbines 46, 54 rotationally drivethe respective low speed spool 30 and high speed spool 32 in response tothe expansion. It will be appreciated that each of the positions of thefan section 22, compressor section 24, combustor section 26, turbinesection 28, and fan drive gear system 48 may be varied. For example,gear system 48 may be located aft of combustor section 26 or even aft ofturbine section 28, and fan section 22 may be positioned forward or aftof the location of gear system 48.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina further example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than about ten (10), thegeared architecture 48 is an epicyclic gear train, such as a planetarygear system or other gear system, with a gear reduction ratio of greaterthan about 2.3 and the low pressure turbine 46 has a pressure ratio thatis greater than about five. In one disclosed embodiment, the engine 20bypass ratio is greater than about ten (10:1), the fan diameter issignificantly larger than that of the low pressure compressor 44, andthe low pressure turbine 46 has a pressure ratio that is greater thanabout five (5:1). Low pressure turbine 46 pressure ratio is pressuremeasured prior to inlet of low pressure turbine 46 as related to thepressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle. The geared architecture 48 may be an epicyclic geartrain, such as a planetary gear system or other gear system, with a gearreduction ratio of greater than about 2.3:1. It should be understood,however, that the above parameters are only exemplary of one embodimentof a geared architecture engine and that the present invention isapplicable to other gas turbine engines including direct driveturbofans.

The example gas turbine engine includes the fan 42 that comprises in onenon-limiting embodiment less than about twenty-six (26) fan blades. Inanother non-limiting embodiment, the fan section 22 includes less thanabout twenty (20) fan blades. Moreover, in one disclosed embodiment thelow pressure turbine 46 includes no more than about six (6) turbinerotors schematically indicated at 34. In another non-limiting exampleembodiment the low pressure turbine 46 includes about three (3) turbinerotors. A ratio between the number of fan blades 42 and the number oflow pressure turbine rotors is between about 3.3 and about 8.6.

The example low pressure turbine 46 provides the driving power to rotatethe fan section 22 and therefore the relationship between the number ofturbine rotors 34 in the low pressure turbine 46 and the number ofblades 42 in the fan section 22 disclose an example gas turbine engine20 with increased power transfer efficiency.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the engine 20 is designedfor a particular flight condition—typically cruise at about 0.8 Mach andabout 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft, withthe engine at its best fuel consumption—also known as “bucket cruiseThrust Specific Fuel Consumption (‘TSFC’)”—is the industry standardparameter of lbm of fuel being burned divided by lbf of thrust theengine produces at that minimum point. “Low fan pressure ratio” is thepressure ratio across the fan blade alone, without a Fan Exit Guide Vane(“FEGV”) system. The low fan pressure ratio as disclosed hereinaccording to one non-limiting embodiment is less than about 1.55. Inanother non-limiting embodiment the low fan pressure ratio is less thanabout 1.45. In another non-limiting embodiment the low fan pressureratio is from 1.1 to 1.45. “Low corrected fan tip speed” is the actualfan tip speed in ft/sec divided by an industry standard temperaturecorrection of [(Tram ° R)/(518.7° R)]^(0.5). The “low corrected fan tipspeed” as disclosed herein according to another non-limiting embodimentis less than about 1200 ft/second.

Referring to FIG. 2A-2C, the fan blade 42 is supported by a fan hub 60that is rotatable about the axis X, which corresponds to the Xdirection. Each fan blade 42 includes an airfoil 64 extending in aradial span direction R from a root 62 to a tip 66. A 0% span positioncorresponds to a section of the airfoil 64 at the inner flow path (e.g.,a platform), and a 100% span position corresponds to a section of theairfoil 64 at the tip 66.

The root 62 is received in a correspondingly shaped slot in the fan hub60. The airfoil 64 extends radially outward of the platform, whichprovides the inner flow path. The platform may be integral with the fanblade or separately secured to the fan hub, for example. A spinner 66 issupported relative to the fan hub 60 to provide an aerodynamic innerflow path into the fan section 22.

The airfoil 64 has an exterior surface 76 providing a contour thatextends from a leading edge 68 aftward in a chord-wise direction H to atrailing edge 70, as shown in FIG. 2C. Pressure and suction sides 72, 74join one another at the leading and trailing edges 68, 70 and are spacedapart from one another in an airfoil thickness direction T. An array ofthe fan blades 42 are positioned about the axis X in a circumferentialor tangential direction Y. Any suitable number of fan blades may be usedin a given application.

The exterior surface 76 of the airfoil 64 generates lift based upon itsgeometry and directs flow along the core flow path C. The fan blade 42may be constructed from a composite material, or an aluminum alloy ortitanium alloy, or a combination of one or more of these.Abrasion-resistant coatings or other protective coatings may be appliedto the fan blade 42. The curves and associated values assume a fan in ahot, running condition (typically cruise).

One characteristic of fan blade performance relates to the fan blade'sleading and trailing edge aerodynamic dihedral angle relative to aparticular span position (R direction). Referring to FIG. 3A, spanpositions a schematically illustrated from 0% to 100% in 10% increments.Each section at a given span position is provided by a conical cut thatcorresponds to the shape of the core flow path, as shown by the largedashed lines. In the case of a fan blade with an integral platform, the0% span position corresponds to the radially innermost location wherethe airfoil meets the fillet joining the airfoil to the platform. In thecase of a fan blade without an integral platform, the 0% span positioncorresponds to the radially innermost location where the discreteplatform meets the exterior surface of the airfoil. In addition tovarying with span, leading and trailing edge sweep varies between a hot,running condition and a cold, static (“on the bench”) condition.

An aerodynamic dihedral angle D (simply referred to as “dihedral”) isschematically illustrated in FIG. 3B for a simple airfoil. Anaxisymmetric stream surface S passes through the airfoil 64 at alocation that corresponds to a span location (FIG. 3A). For the sake ofsimplicity, the dihedral D relates to the angle at which a line L alongthe leading or trailing edge tilts with respect to the stream surface S.A plane P is normal to the line L and forms an angle with the tangentialdirection Y, providing the dihedral D. A positive dihedral D correspondsto the line tilting toward the suction side (suction side-leaning), anda negative dihedral D corresponds to the line tilting toward thepressure side (pressure side-leaning). The method of determining andcalculating the dihedral for more complex airfoil geometries isdisclosed in Smith Jr., Leroy H., and Yeh, Hsuan “Sweep and DihedralEffects in Axial-Flow Turbomachinery.” J. Basic Eng. Vol. 85 Iss. 3, pp.401-414 (Sep. 1, 1963), which is incorporated by reference in itsentirety.

Example relationships between the leading edge dihedral (LE DIHEDRAL)and the span position (LE SPAN %) are shown in FIGS. 4A and 5A forseveral example fan blades, each represented by a curve. Only one curvein each graph is discussed for simplicity. In the examples, the leadingedge dihedral is negative from the 0% span position to the 100% spanposition.

The leading edge dihedral at the 0% span position (92 in FIG. 4A; 104 inFIG. 5A) is in the range of −3° to −12°. In the examples shown in FIGS.4A and 5A, the leading edge dihedral at the 0% span position is about−4°.

The leading edge dihedral extends from the 0% span position to a 20%span position (96 in FIG. 4A; 108 in FIG. 5A) having a leading edgedihedral in a range of −2° to −6°.

In the examples shown in FIGS. 4A and 5A, the leading edge dihedralincludes a first point (100 in FIG. 4A; 110 in FIG. 5A) at a 75% spanposition and extends generally linearly from the first point to a secondpoint (102 in FIG. 4A; 114 in FIG. 5A) at the 85% span position. Thefirst point is in a range of −8° to −10° dihedral, and the second pointis in a range of −3° to −6° dihedral.

Referring to FIG. 4A, a maximum negative dihedral 98 is in a range of95-100% span position. A least negative dihedral 94 is in a range of5-15% span position. Referring to FIG. 5A, a maximum negative dihedral110 is in a range of 65-75% span position. A least negative dihedral 106is in a range of 0-10% span position.

Example relationships between the trailing edge dihedral (TE DIHEDRAL)and the span position (TE SPAN %) are shown in FIGS. 4B and 5B forseveral example fan blades, each represented by a curve. Only one curvein each graph is discussed for simplicity. In the examples, the trailingedge dihedral is positive from the 0% span position to the 100% spanposition. The relationship provides a generally C-shaped curve from the0% span position to a 50% span position and then a 90% span position.

A trailing edge dihedral (130 in FIG. 4B; 140 in FIG. 5B) at the 0% spanposition is in a range of 20° to 25°. A trailing edge dihedral (132 inFIG. 4B; 142 in FIG. 5B) at about the 50% span position is in a range of2° to 6°. A trailing edge dihedral (137 in FIG. 4B; 147 in FIG. 5B) atthe 90% span position is in a range of 16° to 22°. From a 65% spanposition (134 in FIG. 4B; 144 in FIG. 5B) to a 75% span position (136 inFIG. 4B; 146 in FIG. 5B) the trailing edge dihedral increases about 5°.

A positive-most trailing edge dihedral (138 in FIG. 4B; 148 in FIG. 5B)in a 80%-100% span position is within 5° of the trailing edge dihedralin the 0% span position (130 in FIG. 4B; 140 in FIG. 5B). A leastpositive trailing edge dihedral (132 in FIG. 4B; 142 in FIG. 5B) is in a40%-55% span position.

The leading and trailing edge aerodynamic dihedral in a hot, runningcondition along the span of the airfoils 64 relate to the contour of theairfoil and provide necessary fan operation in cruise at the lower,preferential speeds enabled by the geared architecture 48 in order toenhance aerodynamic functionality and thermal efficiency. As usedherein, the hot, running condition is the condition during cruise of thegas turbine engine 20. For example, the leading and trailing edgeaerodynamic dihedral in the hot, running condition can be determined ina known manner using numerical analysis, such as finite elementanalysis.

It should also be understood that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom. Although particular step sequencesare shown, described, and claimed, it should be understood that stepsmay be performed in any order, separated or combined unless otherwiseindicated and will still benefit from the present invention.

Although the different examples have specific components shown in theillustrations, embodiments of this invention are not limited to thoseparticular combinations. It is possible to use some of the components orfeatures from one of the examples in combination with features orcomponents from another one of the examples.

Although an example embodiment has been disclosed, a worker of ordinaryskill in this art would recognize that certain modifications would comewithin the scope of the claims. For that reason, the following claimsshould be studied to determine their true scope and content.

What is claimed is:
 1. An airfoil for a turbine engine comprising: anairfoil having pressure and suction sides extending in a radialdirection from a 0% span position at an inner flow path location to a100% span position at an airfoil tip, wherein the airfoil has arelationship between a leading edge dihedral and a span position, theleading edge dihedral negative from the 0% span position to the 100%span position, wherein a positive dihedral corresponds to suctionside-leaning, and a negative dihedral corresponds to pressureside-leaning; and wherein the airfoil has a relationship between atrailing edge dihedral and a span position, the trailing edge dihedralpositive from the 0% span position to the 100% span position, wherein apositive dihedral corresponds to suction side-leaning, and a negativedihedral corresponds to pressure side-leaning.
 2. The airfoil accordingto claim 1, wherein the leading edge dihedral at the 0% span position isin the range of −3° to −12°.
 3. The airfoil according to claim 2,wherein the leading edge dihedral at the 0% span position is about −4°.4. The airfoil according to claim 2, wherein the leading edge dihedralat the 0% span position is about −10°.
 5. The airfoil according to claim2, wherein the leading edge dihedral extends from the 0% span positionto a 20% span position having a leading edge dihedral in a range of −2°to −6°.
 6. The airfoil according to claim 5, wherein the leading edgedihedral includes a first point at a 75% span position and extendsgenerally linearly from the first point to a second point at the 85%span position.
 7. The airfoil according to claim 6, wherein the firstpoint is in a range of −8° to −10° dihedral.
 8. The airfoil according toclaim 6, wherein the second point is in a range of −3° to −6° dihedral.9. The airfoil according to claim 2, wherein a maximum negative dihedralis in a range of 95-100% span position.
 10. The airfoil according toclaim 9, wherein a least negative dihedral is in a range of 5-15% spanposition.
 11. The airfoil according to claim 2, wherein a maximumnegative dihedral is in a range of 65-75% span position.
 12. The airfoilaccording to claim 11, wherein a least negative dihedral is in a rangeof 0-10% span position.
 13. The airfoil according to claim 2, wherein amaximum negative dihedral is in a range of 50-60% span position.
 14. Theairfoil according to claim 13, wherein the relationship provides agenerally C-shaped curve from the 0% span position to a 50% spanposition and then a 90% span position.
 15. The airfoil according toclaim 14, wherein a trailing edge dihedral at the 0% span position is ina range of 20° to 25°.
 16. The airfoil according to claim 15, wherein atrailing edge dihedral at about the 50% span position is in a range of2° to 6°.
 17. The airfoil according to claim 15, wherein a trailing edgedihedral at the 90% span position is in a range of 16° to 22°.
 18. Theairfoil according to claim 15, wherein from a 65% span position to a 75%span position the trailing edge dihedral increases about 5°.
 19. Theairfoil according to claim 16, wherein a positive-most trailing edgedihedral in a 80%-100% span position is within 5° of the trailing edgedihedral in the 0% span position.
 20. The airfoil according to claim 15,wherein a least positive trailing edge dihedral is in a 40%-55% spanposition.
 21. The airfoil according to claim 14, wherein the airfoil isa fan blade for a gas turbine engine.